<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
  function show(a,b){
      alert('this是：'+this+'\na是:'+a+'\nb是:'+b);
     // alert(this);
  }
  //show(12);//还是window
  show(12,5);
  show.call('abc',12,5);//call可以改变函数执行时的this
    </script>
</head>
<body>

</body>
</html>